Chester Model B Super - DC Motor Capacitor Failure - Help?

[ant1dp]

Hi Guys

My Lovely Model B Super has died, when I press start the motor buzzes and it doesnt spin but if I spin the chuck manually it wants to go but slows quickly, apparently this is a sign that the capacitor has died.  All I can see on the manual is its a 550watt DC motor, so I have no idea how to find a replacement.  Can anyone offer any advice?, im also interested in upgrading the motor if anyone has tried that.  


This vid is interesting £78 for a new variable speed motor.
550w brushless industrial sewing machine servo motor Upgrade.  www.youtube.com/watch?v=XcJnCozqMQ0


Thanks for any advice

[millman]

I think Chester are still trading so it may be worth giving them a call and seeing if they have any capacitors in stock.

[cplmickey]

Are there no markings on the capacitor itself. You're looking for it's capacitance value, given in microfarads or uF. Sometimes printed on the outside or occasionally stamped into the end of the can. Unfortunately the company I used a few years ago seems to have ceased trading but there's plenty of choice out there including this one www.motorcontrolwarehouse.co.uk/single-phase-motor-capacitors.html?cat=270
Ian

[ant1dp]

Thanks for your help. I have contacted Chester Machine Tools and sent them a photo of the motors label but they say they need to see the motor and the capacitor so im going to take it off the lathe tomorrow. Im not sure if I want another Chester model though, ive been to a local store and they tell me they can sell me a similar motor and the capacitors look huge in comparison to the current one.

This is the motor label - Pics of motor and capacitor coming tomorrow.
ibb.co/gznLXn5



BTW - can anyone tell me why my image uploads say Error file exedes 1mb, when they are much smaller?

[SteveW]

Ant1DP,

From the motor image label your motor needs a 75uF capacitor for one speed and a 25uF capacitor for the other speed. These capacitors will need/have an AC voltage rating of typically 450 volts.

Yes totally impenetrable nonsense.

Key: the "uF" equates to micro Farads. The "u" is the nearest UK keyboard match to the "mu" character meaning "micro".

Try a search on Amazon for 75uF and 25uF motor start/run (run/start) capacitors rated 450VAC. Yes I know one capacitor is shown as 250volts but this could explain why you need a new one. Keep it simple and stick to 450VAC. Maybe switching voltage spikes stuffed the lower rated component.

It is likely the smaller capacitor is the 25uF one.

I reported a while back when my compressor motor died and filled my workshop with smoke. A new capacitor cost just over a tenner vice 60+ quid from the excellent Machine Mart spare dept.

[ant1dp]

Apr 10, 2024 17:31:38 GMT SteveW said:

AntiDP,

From the motor image label your motor needs a 75uF capacitor for one speed and a 25uF capacitor for the other speed. These capacitors will need/have an AC voltage rating of typically 450 volts.

Yes totally impenetrable nonsense.

Key: the "uF" equates to micro Farads. The "u" is the nearest UK keyboard match to the "mu" character meaning "micro".

Try a search on Amazon for 75uF and 25uF motor start/run (run/start) capacitors rated 450VAC.

It is likely the smaller capacitor is the 25uF one.

I reported a while back when my compressor motor died and filled my workshop with smoke. A new capacitor cost just over a tenner vice 60+ quid from the excellent Machine Mart spare dept.

Ha ha, you just beat me to it.  Here are the images of the capacitors. Please have a look?
ibb.co/dPyJdxy
ibb.co/W6NjTc1

BTW I got the motor working in reverse which is for the Mill but the Lathe direction will not run, so now im 99% sure a capacitor will fix the job.  Can anyone guess which capacitor is which without me sticking my tongue on the connections to test it

[SteveW]

Ant1DP.

A variation of "RTFM" would be "RTFLOTC".

Your photos clearly identify each capacitor by voltage and capacitance. Unless you're really stuffed for space stick with 450VAC.

Is also worth giving the motor windings a good sniff. If it smell of burnt varnish your motor has been cooked.

QED.

It occurs to add that in my experience when capacitors fail they usually vomit their contents out of a new hole.

[SteveW]

Ant1DP,

I would suggest you replace both capacitors rather than faff about guess which one failed.

If the first capacitor fitted fixes your problem keep the other somewhere safe for when the other lets go.

Edit: just found Try

and

[chris vine]

If you use the four off caps that Steve has linked to, then you can use one as it is for the 75uf one.
For the 25uf, you can use the other three wired in series to achieve the 25uf!
At least you could try it that way to see if it solves the problem...

Chris.

[SteveW]

Apr 10, 2024 20:52:53 GMT chris vine said:

If you use the four off caps that Steve has linked to, then you can use one as it is for the 75uf one.
For the 25uf, you can use the other three wired in series to achieve the 25uf!
At least you could try it that way to see if it solves the problem...

Chris.

Those were just results from my quick search for suitable capacitors and ignore the quantity detail. Four 75uF/450VAC for 18 quid should put the OEM item cost into contrast.

Buying four off 75uF caps would not be the way I'd be going.

One off of each size from one supplier to minimise PnP. Not forgetting Amazon Prime rates if available although contrast the ease of joining Amazon Prime against the nightmare of escaping from it.

Other suppliers available.

Edit: if going for four off 25uF caps wire three in parallel to achieve 75uF but you really don't want two extra capacitors rattling around just looking for a good deal.

[ant1dp]

Thanks so much Steve and Chris, especially for taking the time to help me with the capacitors links too.  Ive been emailing eBay suppliers to ask them to confirm that the capacitors id selected from them were the same as the ones in my photo's and id only got one reply today which said "Sorry but our warehouse doesnt have the stock you need" which just confused me but I think they didnt want to be responsible or something.  
Ive selected the capacitors that Steve linked and im looking forward to replacing them both.  Im going for the 75uf and 20uf because I dont fancy trying to tidy all those capacitors away especially as my motor and caps are directly behind where all the swarf goes.  I should try and build a cover for it.  btw Chester was no use, they just said "you can buy caps on eBay".


The Model B super is a 3 pully system to change speeds and ive always fantasized about putting a variable speed motor in so I could turn at the correct speeds but without my Model B working id dread trying to make it all fit.
I absolutely love my little lathe and mill because I can do all the crazy ideas that pop in my head, making my own parts or modifying to make it suit my own purpose.   I once bought a good 3d printer but I couldnt get on with learning the CAD software even though im a computer pro, id rather make stuff like I turned a Brembo hand brake into a rear thumb brake which is amazing because rear brake MC's are designed to be weak so you cant skid the rear tyre but with the brembo I get all the delicate feeling of a front brake now and its cheaper than any purchasable thumb brake.  


ibb.co/PZYSNBC
ibb.co/HppfCRv

BTW is there a way to post pics on here or is it best to just provide links.  When I try to upload i get a warning that its too big which its not.

[uuu]

I've had a go opening one of your images in IBB. Scrolling down I get a section headed "embed codes" and there's a box with BBCode in it. Copying and pasting into a reply here (not pressing any buttons here - just paste in the code) - I get this :



Wilf

[ant1dp]

Thanks Elder 

I love my Model B to make little parts like this alloy bracket to hold a rear brake above my clutch.  Id prefer a seperate lathe and mill but not much room, maybe one day.

[SteveW]

Guys,

Not forgetting that the thread title and the image of the motor label are at odds.

From the motor label it would appear to be a Single Phase AC motor.

[ant1dp]

Apr 12, 2024 9:28:25 GMT SteveW said:

Guys,

Not forgetting that the thread title and the image of the motor label are at odds.

From the motor label it would appear to be a Single Phase AC motor.

Yes it is but it has to turn in two directions, thats why two caps.  Or am I missing something?

[uuu]

I would not expect the extra capacitor is related to reversing the motor. It may be you have a "capacitor-start-capacitor-run" motor, that uses one capacitor all the time and another only when starting. This would exhibit a characteristic "click" as the motor slows down on turn-off. See description here: www.electricity-magnetism.org/capacitor-start-capacitor-run-induction-motor/

Wilf

[uuu]

In the future you could consider upgrading to a three-phase motor with an inverter to provide variable speed. When I've gone this route I've kept my eyes open on ebay for both motor and inverter (separately) to come up cheaply.

Wilf

[andyhigham]

I use a lot of inverter drives for work. I normally use Invertek drives, they have everything I need without over complexity and zillions of features. PLUS they are made in UK. This is the 0.75Kw (1HP) unit inverterdrive.com/group/AC-Inverter-Drives-230V/Invertek-Optidrive-E3-750W-1ph-3ph-IP20/

[SteveW]

Apr 12, 2024 12:49:35 GMT ant1dp said:

Apr 12, 2024 9:28:25 GMT SteveW said:

Guys,

Not forgetting that the thread title and the image of the motor label are at odds.

From the motor label it would appear to be a Single Phase AC motor.

Yes it is but it has to turn in two directions, thats why two caps.  Or am I missing something?

An AC motor usually has multiple coils the aim being to create a rotating magnetic field that drags the rotor around. With a three phase supply this is easy. Either three coils distributed equally around the inside wired in a star or a triangle (delta) and a power phase connected to each the three ends. The centre of the star connection floats notionally at zero phase.

With a single phase motor/supply an extra phase shifted out of phase, typically 90°, to the supply phase is needed to complete the rotating magnetic field. The capacitor(s) in conjunction with the motor winding inductance achieves this and its important the external capacitance value really should match the motor coil inductance. If the motor label says 25uF one should use a 25uF capacitor else madness can ensue.

Reversing the AC motor direction simply requires that two of the phases are reversed or the equivalent of one of the windings is reversed in a single phase motor. Its why the motor control reversing switch has so many wired going into it.

[andyhigham]

The two capacitors will be start and run